Method and apparatus for packet aggregation in power line communication network

ABSTRACT

A method and apparatus for packet aggregation in a power line communication network (PLC) are provided. The method of aggregating packets includes: by performing a PLC channel estimation, determining whether or not a channel condition is good; if the channel condition is good, determining whether or not the data desired to be transmitted is suitable for packet aggregation according to the type of data; and if the channel condition is good and the data desired to be transmitted is suitable for the packet aggregation, aggregating packets of the data desired to be transmitted. Since a decision on whether or not to aggregate packets is determined according to a channel condition at a physical level and the type of data at an application level, packet aggregation can be performed in appropriate response to the frequently changing condition of a channel and the characteristic of the data desired to be transmitted.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a National Stage Entry of PCT/KR2006/004595, filedon Nov. 6, 2006, which claims the benefit of Korean Patent ApplicationNo. 10-2006-0015157, filed on Feb. 16, 2006, in the Korean IntellectualProperty Office, the disclosures of which are incorporated herein intheir entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power line communication (PLC), andmore particularly, to a packet aggregation method and apparatus in a PLCnetwork.

2. Description of the Related Art

A power line communication (PLC) network is one of a plurality of localcommunication networks. PLC technology uses existing power lines inhouses. Accordingly, unlike Ethernet, a PLC network does not needadditional wiring, and can be used in basements or shaded areas thatwireless technology cannot reach.

Packets transmitted through a network include header information fortransmission control, flow control and link control, in addition to datadesired to be transmitted. This header information lowers the efficiencyof data transmission through a network. To address this problem, apacket aggregation technique is used.

However, since it is difficult to apply an ordinary packet aggregationtechnique used in a wireless local area network (WLAN) directly to a PLCnetwork, a packet aggregation technique suitable for a PLC network isneeded.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for packetaggregation that can be applied to a power line communication (PLC)network.

The present invention also provides a computer readable recording mediumhaving embodied thereon a computer program for executing the packetaggregation method.

According to an aspect of the present invention, there is provided amethod of aggregating packets in a power line communication (PLC)network including: by performing a PLC channel estimation, determiningwhether or not a channel condition is good; if the channel condition isgood, determining whether or not the data desired to be transmitted issuitable for packet aggregation according to the type of data; and ifthe channel condition is good and the data desired to be transmitted issuitable for the packet aggregation, aggregating packets of the datadesired to be transmitted.

According to another aspect of the present invention, there is providedan apparatus for packet aggregation in a power line communication (PLC)network, including: a channel condition determination unit thatdetermines whether or not a channel condition is good by performing aPLC channel estimation; a data type determination unit that, if thechannel condition is good, determines whether or not a data desired tobe transmitted is suitable for packet aggregation according to the typeof data; and a packet aggregation unit that aggregates packets of thedata desired to be transmitted if the channel condition is good and thedata desired to be transmitted is suitable for the packet aggregation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 illustrates an example of applying packet aggregation to datapackets; and

FIG. 2 is a flowchart illustrating a method of aggregating packetsaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown.

FIG. 1 illustrates an example of applying packet aggregation to datapackets.

A medium access control (MAC) layer performs an important role in anetwork. MAC technology in a power line communication (PLC) networkemploys a carrier sense multiple access/collision avoidance (CSMA/CA)method in the same way as a wireless local area network (WLAN) does.That is, not only is data transmitted through a transmission medium, butalso header information for transmission control, flow control, or linkcontrol is transmitted. For header information, a separate frame isused, or a separate field is assigned in a frame.

Frequent transfers of this header information lower an overallefficiency of the MAC layer. In order to enhance the data transmissionefficiency of the MAC layer, packet aggregation is used.

Packet aggregation is performed as follows. Referring to FIG. 1, datapackets having common header information 10 through 1N are collected inoperation 100, and common headers 11 through 1N are removed in operation110 leaving the first common header 10. Then, by sequentially connectingthe collected data 20 through 2N to the common header 10, one datapacket is generated in operation 120.

By performing packet aggregation, network resources required forrepeatedly transmitting common header information can be saved.

FIG. 2 is a flowchart illustrating a method of aggregating packetsaccording to an embodiment of the present invention.

Generally, it is important to determine which packet the packetaggregation is applied to.

Uniform application of packet aggregation cannot guarantee quality ofservice (QoS). Since a required delay or bandwidth varies with respectto an application, it is inefficient to uniformly apply packetaggregation. Also, a channel condition changes frequently in a PLCenvironment. In the present invention, a packet aggregation method whichselectively applies packet aggregation reflecting the characteristic ofa channel and QoS requirement information of an application in a PLCnetwork is suggested.

In the packet aggregation method according to the current embodiment ofthe present invention, two variables are considered. One is a channelcondition at a physical (PHY) level, and the other is the characteristicof an application at an application level.

In order to identify a channel condition at the PHY level, channelestimation is performed in operation S100. By using the result of thechannel estimation, it is determined whether or not the channelcondition is good in operation S110.

In order to measure the channel condition at the PHY level, an availablebandwidth of a channel is calculated by using a predetermined formula.

If an apparatus for performing the packet aggregation method accordingto the current embodiment of the present invention, that is, anapparatus performing PLC channel estimation, is using a channel, theavailable bandwidth of the channel is calculated by using the followingequation 1:

B_(Rcv,i)×P_(Success,i)×(T_(Hold,i)+T_(Rest))  (1)

where B_(Rcv,i) is the modulation bit rate of a packet received by theapparatus performing the PLC channel estimation during communication,P_(Success,i) is a ratio that a packet received by the apparatusperforming the PLC channel estimation is decoded without errors duringcommunication, T_(Hold,i) is a time ratio that the apparatus performingthe PLC channel estimation occupies the channel, and T_(Rest) is a timeratio that no apparatus uses the channel.

When no apparatus in the PLC network communicates, the availablebandwidth of the channel is calculated by using the following equation2:

B_(Max)  (2)

where B_(Max) is the maximum modulation bit rate in a system.

When the apparatus performing the PLC channel estimation does not usethe channel and other PLC apparatuses are using the channel forcommunication, the available bandwidth of the channel is calculated byusing the following equation 3:

$\begin{matrix}{T_{Rest} \times \frac{\sum\limits_{j = 0}^{N - 1}\left\lbrack {B_{{Rcv},j} \times P_{{Success},j} \times T_{{Hold},j}} \right\rbrack}{\sum\limits_{j = 0}^{N - 1}T_{{Hold},j}}} & (3)\end{matrix}$

where N is a number of modulation methods used in the PLC network,T_(Rest) is a time ratio that no apparatus uses the channel, B_(Rcv,j)is a modulation bit rate of a packet modulated using a j-th modulationmethod among N modulation methods, T_(Success,j) is a ratio that apacket modulated using a j-th modulation method among N modulationmethods is decoded without errors, and T_(Hold,j) is a time ratio that apacket modulated using a j-th modulation method uses the channel.

After the available bandwidth of the channel is calculated according tothe equations described above, if the calculated bandwidth is equal toor greater than a reference bandwidth, it is determined that the channelcondition is good.

If the channel condition is not good, packet aggregation is notperformed and ordinary data transmission is performed in operation S140.

If the channel condition is good, it is determined whether or not packetaggregation is applied with respect to the characteristics of anapplication at an application level in operation S120.

In an embodiment of the present invention, types of data are dividedinto class A type and class B type. Class A type data has a large packetsize for data desired to be transmitted, and a maximum delay requirementin a network is long. The maximum delay requirement is a requirementthat a maximum delay in a network should be equal to or less than apredetermined value. In the case of class A type data, since the maximumdelay requirement is long, a long delay in a network is acceptable.Accordingly, class A type data is suitable for packet aggregation.Examples of class A type data include content for high definitiontelevisions (HDTVs), and MPEG data. If the data desired to betransmitted is class A type data, packet aggregation is performed inoperation S130 and the data is transmitted in operation S140.

Class B type data has a small packet size for data desired to betransmitted, and a maximum delay requirement in a network is short.Accordingly, a long delay in a network is not acceptable for class Btype data. If packet aggregation is applied to Class B type data, adelay in a network occurs. Accordingly, class B type data is notsuitable for packet aggregation. Examples of class B type data includedata for voice over Internet protocol (VoIP), and contents forinteractive games.

If the data desired to be transmitted is class B type data, packetaggregation is not performed and ordinary data transmission is performedin operation S140.

As described above, since the decision to aggregate packets isdetermined according to the channel condition at a physical level andthe type of data at an application level, packet aggregation can beperformed in appropriate response to the frequently changing conditionof a channel and the characteristic of the data desired to betransmitted. Accordingly, by using the packet aggregation methodaccording to the current embodiment of the present invention, thetransmission efficiency of the channel can be enhanced and the qualityof service (QoS) can be guaranteed compared to a conventional packetaggregation method in which packet aggregation is uniformly applied.

The present invention can also be embodied as computer readable codes ona computer readable recording medium. The computer readable recordingmedium is any data storage device that can store data which can bethereafter read by a computer system. Examples of the computer readablerecording medium include read-only memory (ROM), random-access memory(RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data storagedevices.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims. Thepreferred embodiments should be considered in descriptive sense only andnot for purposes of limitation. Therefore, the scope of the invention isdefined not by the detailed description of the invention but by theappended claims, and all differences within the scope will be construedas being included in the present invention.

According to the method and apparatus for packet aggregation in a PLCnetwork of the present invention, since a decision on whether or not toaggregate packets is determined according to the channel condition at aphysical level and the type of data at an application level, packetaggregation can be performed in appropriate response to the frequentlychanging condition of a channel and the characteristic of the datadesired to be transmitted. Accordingly, transmission efficiency of thechannel can be enhanced and quality of service (QoS) can be guaranteedcompared to a conventional packet aggregation method in which packetaggregation is uniformly applied.

1. A method of aggregating packets in a power line communication (PLC)network comprising: by performing a PLC channel estimation, determiningwhether or not a channel condition is good; if the channel condition isgood, determining whether or not the data desired to be transmitted issuitable for packet aggregation according to the type of data; and ifthe channel condition is good and the data desired to be transmitted issuitable for the packet aggregation, aggregating packets of the datadesired to be transmitted.
 2. The method of claim 1, wherein thedetermining of whether or not the channel condition is good comprises:calculating the available bandwidth of the channel by using apredetermined formula according to whether or not an apparatusperforming the PLC channel estimation uses a channel; and if theavailable bandwidth of the channel is equal to or greater than areference bandwidth, determining that the channel condition is good. 3.The method of claim 2, wherein the calculating of the availablebandwidth of the channel comprises calculating the available bandwidthof the channel by using the following formula if the apparatusperforming the PLC channel estimation communicates by using the channel:B_(Rcv,i)×P_(Success,i)×(T_(Hold,i)+T_(Rest)) where B_(Rcv,i) is themodulation bit rate of a packet received by the apparatus performing thePLC channel estimation during communication, P_(Success,i) is a ratiothat a packet received by the apparatus performing the PLC channelestimation is decoded without errors during communication, T_(Hold,i) isa time ratio that the apparatus performing the PLC channel estimationoccupies the channel, and T_(Rest) is a time ratio that no apparatususes the channel.
 4. The method of claim 2, wherein the calculating ofthe available bandwidth of the channel comprises determining a maximummodulation bit rate as the available bandwidth of the channel when noapparatus in the PLC network performs communication.
 5. The method ofclaim 2, wherein the calculating of the available bandwidth of thechannel comprises calculating the available bandwidth of the channel byusing the following formula if the apparatus performing the PLC channelestimation does not use the channel and other PLC apparatuses use thechannel:$T_{Rest} \times \frac{\sum\limits_{j = 0}^{N - 1}\left\lbrack {B_{{Rcv},j} \times P_{{Success},j} \times T_{{Hold},j}} \right\rbrack}{\sum\limits_{j = 0}^{N - 1}T_{{Hold},j}}$where N is a number of modulation methods used in the PLC network,T_(Rest) is a time ratio that no apparatus uses the channel, B_(Rcv,j)is a modulation bit rate of a packet modulated using a j-th modulationmethod among N modulation methods, T_(Success,j) is a ratio that apacket modulated using a j-th modulation method among N modulationmethods is decoded without errors, and T_(Hold,j) is a time ratio that apacket modulated using a j-th modulation method uses the channel.
 6. Themethod of claim 1, wherein the determining of whether or not the datadesired to be transmitted is suitable for packet aggregation comprises,if the type of data has a large packet size and accepts a long delay ina network, determining that the data desired to be transmitted issuitable for packet aggregation.
 7. The method of claim 6, wherein thedata desired to be transmitted is content for high definitiontelevisions (HDTVs) or MPEG data.
 8. The method of claim 1, wherein thedetermining of whether or not the data desired to be transmitted issuitable for packet aggregation comprises, if the type of data has asmall packet size and does not accept a long delay in a network,determining that the data desired to be transmitted is not suitable forpacket aggregation.
 9. The method of claim 8, wherein the data desiredto be transmitted is data for voice over Internet protocol (VoIP) orcontent for interactive games.
 10. The method of claim 1, wherein theaggregating of packets of the data desired to be transmitted comprises:collecting data packets having common header information; removingcommon headers of the data packets, excluding a first header; and byconnecting the collected data packets sequentially to the first header,generating a single data packet.
 11. An apparatus for packet aggregationin a power line communication (PLC) network, comprising: a channelcondition determination unit that, determines whether or not a channelcondition is good by performing a PLC channel estimation; a data typedetermination unit that, if the channel condition is good, determineswhether or not a data desired to be transmitted is suitable for packetaggregation according to the type of data; and a packet aggregation unitthat aggregates packets of the data desired to be transmitted if thechannel condition is good and the data desired to be transmitted issuitable for the packet aggregation.
 12. The apparatus of claim 11,wherein the channel condition determination unit comprises: a bandwidthcalculation unit that calculates the available bandwidth of the channelby using a predetermined formula according to whether or not theapparatus uses a channel; and a bandwidth comparison unit that, if theavailable bandwidth of the channel is equal to or greater than areference bandwidth, determines that the channel condition is good. 13.The apparatus of claim 12, wherein, if the apparatus performscommunication by using the channel, the bandwidth calculation unitcalculates the available bandwidth of the channel by using the followingformula:B_(Rcv,i)×P_(Success,i)×(T_(Hold,i)+T_(Rest)) where B_(Rcv,i) is themodulation bit rate of a packet received by the apparatus performing thePLC channel estimation during communication, P_(Success,i) is a ratiothat a packet received by the apparatus performing the PLC channelestimation is decoded without errors during communication, T_(Hold,i) isa time ratio that the apparatus performing the PLC channel estimationoccupies the channel, and T_(Rest) is a time ratio that no apparatususes the channel.
 14. The apparatus of claim 12, wherein, when noapparatus in the PLC network communicates, the bandwidth calculationunit determines a maximum modulation bit rate as the available bandwidthof the channel.
 15. The apparatus of claim 12, wherein, if the apparatusdoes not use the channel but other PLC apparatuses use the channel, thebandwidth calculation unit calculates the available bandwidth of thechannel by using the following formula:$T_{Rest} \times \frac{\sum\limits_{j = 0}^{N - 1}\left\lbrack {B_{{Rcv},j} \times P_{{Success},j} \times T_{{Hold},j}} \right\rbrack}{\sum\limits_{j = 0}^{N - 1}T_{{Hold},j}}$where N is a number of modulation methods used in the PLC network,T_(Rest) is a time ratio that no apparatus uses the channel, B_(Rcv,j)is a modulation bit rate of a packet modulated using a j-th modulationmethod among N modulation methods, T_(Success,j) is a ratio that apacket modulated using a j-th modulation method among N modulationmethods is decoded without errors, and T_(Hold,j) is a time ratio that apacket modulated using a j-th modulation method uses the channel. 16.The apparatus of claim 11, wherein, if the type of data has a largepacket size and accepts a long delay in a network, the data typedetermination unit determines that the data desired to be transmitted issuitable for packet aggregation.
 17. The apparatus of claim 16, whereinthe data desired to be transmitted is content for high definitiontelevisions (HDTVs) or MPEG data.
 18. The apparatus of claim 11,wherein, if the type of data has a small packet size and does not accepta long delay in a network, the data type determination unit determinesthat the type of the data desired to be transmitted is not suitable forpacket aggregation.
 19. The apparatus of claim 18, wherein the datadesired to be transmitted is data for voice over Internet protocol(VoIP) or content for interactive games.
 20. The apparatus of claim 11,wherein the packet aggregation unit comprises: a data collecting unitthat collects data packets having common header information; a headerremoval unit that removes common headers of the data packets, excludinga first header; and an aggregated packet generation unit that generatesa single data packet, by connecting the collected data packetssequentially to the first header.
 21. A computer readable recordingmedium having embodied thereon a computer program for executing a methodof aggregating packets in a power line communication (PLC) network,wherein the method comprises: by performing a PLC channel estimation,determining whether or not a channel condition is good; if the channelcondition is good, determining whether or not the data desired to betransmitted is suitable for packet aggregation according to the type ofdata; and if the channel condition is good and the data desired to betransmitted is suitable for the packet aggregation, aggregating packetsof the data desired to be transmitted.